As far as I know, noone has explored whether the deccan traps eruption was the result of an iron meteor strike that actually shattered the crust of the earth. That would explain the unique flow patterns (and the size) of that feature.
Yeah, good point... the Deccan Traps were saddled on as the volcanic source for the clouds of crud that snuffed out the dinos -- but this was rejected, partly due to the Alvarez theory bandwagon effect, and mostly because the Traps were formed over such a long period (i.e, they weren't all erupting at the same time). The idea that all the volcanoes in the world simultaneously erupted at the KT boundary -- something that was put forward ad hoc without any basis in the data -- begged the question, "what made all of them erupt"? In recent years, someone (a slow-extinction, no "Great Dying" advocate?) did an alleged study claiming that large impacts wouldn't trigger such eruptions. (':